1. Field of the Invention
The present invention relates to a concrete fence constructed of individual panels of steel reinforced concrete. The panels are made so thin that they do not conform to the American Concrete Institute""s standards for concrete thickness for protection for reinforcement. These panels are secured in the ground so that the panels align with each other to form a fence. A fence constructed of these panels will visibly deflect when the design loading is applied to the fence and will resume its original configuration when the loading is removed without damaging either the reinforcing steel or the concrete skin on the reinforcing steel.
2. Description of the Related Art
Concrete panels are used for various purposes, including fencing material. The concrete panels that are currently in use for fencing material are designed so that wind forces impacting the fence will not cause the concrete panels to noticeably deflect. These prior art concrete panels have been constructed so that the panels remain rigid, even under maximum design loading.
One of the standards that specifies the thickness of concrete to be used in steel reinforced concrete panels is the American Concrete Institute (ACI) standard for concrete protection for reinforcement. The ACI standard for concrete cover as protection of reinforcement against earth or weather and other effects is measured from the concrete surface to the outermost surface of the steel to which the cover requirements applies. Currently, under the ACI standard (ACI 318-77), the minimum concrete cover of reinforcement for pre-cast concrete wall panels that are exposed to earth or weather is xc2xe inches of concrete surrounding the reinforcement for no. 11 bar and smaller.
The present invention is constructed of steel reinforced concrete panels that are made very thin so that they contain so little concrete that they do not satisfy the ACI standard for minimum concrete cover of reinforcement for pre-cast concrete wall panels that are exposed to earth or weather. These ACI standards are published by the American Concrete Institute and can be obtained from that organization which can be reached at the following address: American Concrete Institute, Box 19150, Redford Station, Detroit, Mich. 48219.
A fence constructed of these very thin panels is lighter in weight than conventional concrete fence panels, making it less expensive to manufacture and easier and less expensive to transport and install.
Current wisdom says that steel reinforced concrete wall panels should be rigid, even under maximum load conditions. The present invention does not remain rigid under maximum load conditions, but instead bends or deflects visibly. The panels of the present invention remain in the elastic range even under maximum load conditions so that the panels return to their original pre-deflection configuration when the load is removed. The unexpected thing about the present invention is that the concrete does not crack as a result of the deflection the panels undergo. Instead, the thin concrete skin flexes with the underlying reinforcing steel bars. The reinforcing steel bars extend longitudinally within each panel and primarily provide the structural strength to the panel, although the thin concrete skin does provide a stiffness contribution.
The present invention is a concrete silt fence constructed of a plurality of very thin steel reinforced concrete panels that are aligned side by side and secured in the ground to form a fence. The panels may be fixed in a trench in the ground by backfilling and compacting fine granular material against the lower ends and sides of the panels or by placing concrete around the lower ends and sides of the panels to fill the trench. The fence may be used to retain silt or for other purposes, such as for example security fences or privacy fences.
Each of the panels is constructed of reinforcing steel bars and concrete. The steel bars are aligned parallel to each other and parallel with the longitudinal axis of the panel. A steel bar is provided adjacent each of the two side walls of the panel to provide shear strength to the side edges of the panel, and one or more steel bars are provided between these two outside steel bars. A thin coating of concrete is placed around the reinforcing steel bars so that each pre-cast panel contains so little concrete that it does not satisfy the ACI standard for minimum concrete cover of reinforcement for pre-cast concrete wall panels that are exposed to earth or weather, i.e. does not have xc2xe inch of concrete covering the reinforcing steel bars for no. 11 bar and smaller.
The present invention does not remain rigid under maximum design load conditions, but instead bends or deflects visibly. The panels of the present invention remain in the elastic range even under maximum design load conditions so that the panels return to their original pre-deflection configuration when the load is removed and the concrete does not crack as a result of the deflection the panels undergo. Instead, the thin concrete skin flexes with the underlying reinforcing steel bars. The reinforcing steel bars extend longitudinally within each panel and generally provide the structural strength to the panel, although the thin concrete skin does provide a stiffness contribution.